U.S. Provisional Application No. 60/963,908, filed Aug. 7, 2007, is incorporated herein in its entirety by reference.
An agricultural combine generally includes a header mechanism that severs and collects crop material as the combine is driven through a field, and a feeder mechanism that feeds the crop material to a threshing system or mechanism in the combine. The threshing mechanism includes a rotor assembly. The rotor assembly may include one or more rotatable rotors or tubes. The crop material is threshed as it passes between the rotating rotor or tube and a cylindrical housing or cage of the rotor assembly, the housing or cage having an arrangement of concaves, separator grates, and covers, of which, at least the concaves and grates have apertures for the passage of grain, and elements of material other than grain (MOG), to a cleaning system of the combine.
Typically, the rotor has a front portion, a rear portion and an outer surface that is spaced proximate the cylindrical housing. Reference as examples, old designs such as disclosed in McClung, U.S. Pat. No. 234,599, issued Nov. 16, 1880, and Geiser, U.S. Pat. No. 516,926, issued Mar. 20, 1894; and more modern designs, including Strong et al., U.S. Pat. No. 4,889,517, issued Dec. 26, 1989; Cromheecke et al., U.S. Pat. No. 4,964,838, issued Oct. 23, 1990, (both of which are twin rotor designs); Tanis et al., U.S. Pat. No. 6,325,714, issued Dec. 4, 2001; and Amann et al., U.S. Pat. No. 6,375,564, issued Apr. 23, 2002 (single rotor designs). Generally, on a rotor a number of discrete, outwardly extending elements for threshing and/or separating the crop, secured to the outer surface in one or more predetermined patterns, typically helical patterns. As the rotor rotates, crop material enters the space between the rotor and the housing and is formed into a mat. This mat of crop material contains grain attached to crop heads or ears, and is circulated in a helical manner through the space, by the rotation of the rotor and the elements, typically in cooperation with guide vanes on the inner surface of the cylindrical housing. The speed of rotation of the rotor can range from a few hundred revolutions per minute, to over a thousand. As the crop mat is circulated through the space, it will be initially threshed, largely by the elements configured for threshing, which typically comprise rasp bars of some configuration for essentially raking the material against the inner surface of the housing or cage, to release the grain from the crop material. The released grain will be separated from the MOG for passage through the apertures of the concave and grates to a cleaning system of the combine, as facilitated in large part by the separating elements or bars, which on some rotors are wider than the rasp bars relative to the direction of rotation, as illustrated in Tanis et al., U.S. Pat. No. 6,325,714. Some of the rasp bars may comprise wider bars also. Thus, it has been found that, as the material passes through the space, the threshing and separation needs will vary with position along the rotor. Typically, a high density of threshing elements will be needed to ensure adequate threshing, but may not be needed for separating. The largely grain free MOG will then be ejected from the rear end of the assembly, for discharge from the combine. Here, it should be noted that the terms “front” and “rear” are used merely as directional references, and are not intended to be limiting in regard to the rotor assembly of the present invention, or to the possible orientations of the rotor or rotor assembly in the combine or otherwise.
As addressed in the above referenced Tanis et al. U.S. Pat. No. 6,325,714, crop material sometimes has a tendency to form clumps against elongated threshing and separating elements, which can make their use disadvantageous. In addition, in configurations where two elongated threshing or separating elements are arranged along the same line, a roll of crop material may form against the multiple elongated elements, which is also a disadvantage. Disadvantages of such clumping and formation of rolls is that they can affect the capacity of the rotor assembly, namely, by reducing it. Further, when the rotor encounters clumps or rolls of material, increased power may be required to maintain a normal threshing operation. This increased power requirement can result in a torque spike in the rotor, which generally tends to decrease the effective life of the rotor and, possibly, of the rotor drive. Also, if a high density of elements exists throughout the space between the rotor and housing, excessive amounts of power may be consumed unnecessarily. Conversely, if the density of elements is too low, insufficient threshing can occur and high grain loss experienced.
What is sought therefore, is a rotor assembly which overcomes one or more of the problems and disadvantages set forth above, namely, clumping and rolling of crop material, excessive power consumption and spikes, and inefficient threshing and grain loss.